The present invention relates to a laser beam irradiation device for irradiating a fan-shaped laser beam, and in particular, to a laser beam irradiation device by which it is possible to change a spreading angle of the fan-shaped laser beam irradiated from the device.
In the past, a method for projecting a fan-shaped laser beam has been known. According to this method, a diverging light beam emitted from a laser light source passes through a cylindrical lens, and a luminous flux of a laser beam is turned to a fan-like shape by refractive power caused by a curved surface of the cylindrical lens.
In general, there are such requirements on the fan-shaped laser beam that the luminous flux has spreading but must be as thin as possible. However, in the fan-shaped laser beam provided by a conventional type laser beam irradiation device, the diverging light passes through the cylindrical lens. When the light beam is projected for a long distance, the light beam is diffused in a thickness direction, i.e. in the direction of its thickness, and becomes thicker. Accordingly, the fan-shaped laser beam projected by the conventional type laser beam irradiation device is very useful for the application at a near distance. However, for the application at a long distance, the fan-shaped laser beam is spread widely and luminance is decreased. Also, the thickness of the fan-shaped laser beam is increased, and inconveniences arise practically when it is used for forming a reference line. Further, the spreading angle is fixed in the conventional case. For instance, when a larger spreading angle is required for the application at a near distance or when there is a request to reduce the spreading angle for the application at a long distance, the conventional type device cannot meet the requirements.
It is an object of the present invention to provide a laser beam irradiation device, by which it is possible to change a spreading angle of a laser beam and to keep a thickness of a fan-shaped laser beam in a thin condition even for the application at a long distance.
To attain the above object, the laser beam irradiation device according to the present invention comprises a light source for emitting a laser beam, a cylindrical lens, an optical system for entering the laser beam to the cylindrical lens perpendicularly with respect to a center line of the cylindrical lens, and a luminous flux rotating means for rotating the incident laser beam around an optical axis of the laser beam. Also, the present invention provides the laser beam irradiation device as described above, wherein the optical system comprises a condenser lens for entering a parallel flux to the cylindrical lens. Further, the present invention provides the laser beam irradiation device as described above, wherein the optical system enters the laser beam to the cylindrical lens perpendicularly with respect to the center line after the laser beam passes through the cylindrical lens in parallel to the center line of the cylindrical lens, and wherein the optical system comprises a corner cube prism and a pentagonal prism. Also, the present invention provides the laser beam irradiation device as described above, wherein the optical system comprises a rhombic prism for moving the optical axis in a parallel direction, and a pentagonal prism for entering the laser beam projected from the rhombic prism to the cylindrical lens perpendicularly with respect to the center line. Further, the present invention provides the laser beam irradiation device as described above, wherein the luminous flux rotating means is designed in such manner that the prism holder for holding the optical system is rotated around the center line of the cylindrical lens.